<p>This study explores the effects of three green modifiers—Crumb Rubber (CR), Fly Ash (FA), and Waste Cooking Oil (WCO)—on the performance and environmental benefits of asphalt binders. A response surface experimental design was used to optimize the dosages of these modifiers, and their rheological properties, high-temperature performance, and low-temperature performance were tested. The study also evaluated the water stability, high-temperature, and low-temperature performance of the composite modified asphalt mixtures in actual construction environments. Additionally, smoke emissions and carbon emissions during production, transportation, and construction were analyzed using Life Cycle Assessment (LCA). The results show that the interactions between CR, FA, and WCO greatly influence asphalt performance. The optimal ratios were found to be 20.0% CR, 5.92% FA, and 10.0% WCO. This ternary modifier improved asphalt elasticity and enhanced high-temperature rutting resistance, as evidenced by rheological test results indicating reduced phase angle and improved deformation resistance. The composite modified asphalt exhibited superior high-temperature shear deformation resistance and flexibility. It also showed excellent freeze-thaw splitting, high-temperature, and low-temperature performance. The splitting strength ratio after freeze-thaw cycles reached 91.5%, significantly higher than conventional asphalt. Environmental assessments revealed that the ternary composite modified asphalt reduced VOCs and Total Volatile Organic Compounds (TVOCs) emissions, particularly at high temperatures, and showed lower carbon emissions compared to conventional asphalt. This research offers insights into the sustainable use of waste materials in asphalt and supports the development of environmentally friendly, high-performance road construction materials.</p>